Forest fragmentation and edge effects from deforestation and selective logging in the Brazilian Amazon

Eben N. Broadbent, Gregory P. Asner, Michael Keller, David E. Knapp, Paulo J.C. Oliveira, Jose N. Silva

Research output: Contribution to journalArticle

248 Citations (Scopus)

Abstract

Forest fragmentation results from deforestation and disturbance, with subsequent edge effects extending deep into remaining forest areas. No study has quantified the effects of both deforestation and selective logging, separately and combined, on forest fragmentation and edge effects over large regions. The main objectives of this study were to: (1) quantify the rates and extent of forest fragmentation from deforestation and logging within the Brazilian Amazon, and (2) contextualize the spatio-temporal dynamics of this forest fragmentation through a literature review of potential ecological repercussions of edge creation. Using GIS and remote sensing, we quantified forest fragmentation - defined as both increases in the forest edge-to-area ratio and number of forest fragments - and edge-effected forest occurring from these activities across more than 1.1 million km2 of the Brazilian Amazon from 1999 to 2002. Annually, deforestation and logging generated ∼32,000 and 38,000 km of new forest edge while increasing the edge-to-area ratio of remaining forest by 0.14 and 0.15, respectively. Combined deforestation and logging increased the edge-to-area ratio of remaining forest by 65% over our study period, while generating 5539 and 3383 new forest fragments, respectively. Although we found that 90% of individual forest fragments were smaller than 4 km2, we also found that 50% of the remaining intact forests were located in contiguous forest areas greater than 35,000 km2. We then conducted a literature review documenting 146 edge effects and found that these penetrated to a median distance of 100 m, a distance encompassing 6.4% of all remaining forests in our study region in the year 2002, while 53% of forests were located within two km of an edge. Annually deforestation and logging increased the proportion of edge-forest by 0.8% and 3.1%, respectively. As a result of both activities, the total proportion of edge-forest increased by 2.6% per year, while the proportion within 100-m increased by 0.5%. Over our study period, deforestation resulted in an additional ∼3000 km2 of edge-forest, whereas logging generated ∼20,000 km2, as it extended deep into intact forest areas. These results show the large extent and rapid expansion of previously unquantified soft-edges throughout the Amazon and highlight the need for greater research into their ecological impacts.

Original languageEnglish (US)
Pages (from-to)1745-1757
Number of pages13
JournalBiological Conservation
Volume141
Issue number7
DOIs
StatePublished - Jul 1 2008
Externally publishedYes

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selective logging
edge effect
deforestation
edge effects
habitat fragmentation
logging
fragmentation
forest edge
literature review
remote sensing
ecological impact

Keywords

  • Forest core
  • Forest texture
  • Landscape ecology
  • Rainforest
  • Remote sensing
  • Sustainability

ASJC Scopus subject areas

  • Ecology, Evolution, Behavior and Systematics
  • Nature and Landscape Conservation

Cite this

Forest fragmentation and edge effects from deforestation and selective logging in the Brazilian Amazon. / Broadbent, Eben N.; Asner, Gregory P.; Keller, Michael; Knapp, David E.; Oliveira, Paulo J.C.; Silva, Jose N.

In: Biological Conservation, Vol. 141, No. 7, 01.07.2008, p. 1745-1757.

Research output: Contribution to journalArticle

Broadbent, Eben N. ; Asner, Gregory P. ; Keller, Michael ; Knapp, David E. ; Oliveira, Paulo J.C. ; Silva, Jose N. / Forest fragmentation and edge effects from deforestation and selective logging in the Brazilian Amazon. In: Biological Conservation. 2008 ; Vol. 141, No. 7. pp. 1745-1757.
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